DESCRIPTION (applicant's abstract): The Achilles heel of most current high-throughput screening (HTS) strategies is the inherent inefficiencies of the available screening assay platforms, leading to excessive rates of false positive and false negative selection. To address the need for more efficient screening assay platforms, we have developed a series of universal biosensors-based on engineered beta-lactamases which can be adapted for activation or inactivation by virtually any protein-protein or protein-ligand interaction that occurs naturally in cells, including those that are modulated by post-translational modifications such as phosphorylation. Thus for rapid and efficient selection of inhibitors of any interaction of interest from large natural or synthetic compound libraries, our engineered beta-lactamases may be set up to be quantitatively inhibited by the target interaction, so that a robust positive signal is produced in the presence of even modest amounts of an inhibitor. In Phase I we will develop a beta-lactamase biosensor for positive signal detection in tumor cells of inhibitors of the phosphorylation-dependent interaction between the signaling protein Grb2 and the oncogenic growth factor receptor ErbB2. In Phase II we will use this biosensor to screen the NCI natural products library, and we will develop additional biosensors. PROPOSED COMMERCIAL APPLICATION: The primary goal of this work is to accelerate the drug discovery process for cancer chemotherapy.